Reciprocating engines and pumps heretofore have been constructed with cylindrical pistons riding in fixed cylinder walls connected to a crankshaft by relatively long connecting rods. Due to the cylindrical nature of their construction and the space taking connecting rods, none of these devices can provide a machine which can process a maximum amount of air for its size and weight and yet be efficient. It has heretofore been known that cube or box shaped structures are very efficient for a given volume, but heretofore this principle has not been employed in engine design. Also prior art engines and pumps are mechanically stressed during operation to such an extent that ceramic or other heat resistant materials cannot be used successfully therewith. Therefore, they must be operated at relatively low temperatures, which result in low efficiencies.